User interface devices are generally configured to accept user operations via a mechanical switch or a touch panel.
When a mechanical switch is used, irregularities are generated on the surface of a device, which may impair the design of the device. In addition, operations based on user's gestures may not be performed by using mechanical switches.
On the other hand, when a touch panel is used, operations may be performed based on a user's gestures. However, touch panels are relatively expensive, which may pose a cost problem. Since touch panels are always in a sensing state, the current consumption increases.